This invention relates to cannulae, more specifically to cannulae used in the introduction of intravenous, intramuscular, intraarterial or other intracorporeal catheters or tubular devices into bodies and has to do with their manufacture.
Such a cannula is located at the insertion end of the catheter where it is used to make the puncture through which the catheter is inserted into a body. A problem in the art has been presented by the need for removal of the cannula after the catheter has been inserted. The cannula being very sharp can cause damage to the catheter or to body tissue if left in place.
One approach to the problem has involved the use of a through-the-cannula catheter in which a cannula is positioned as a sleeve around the insertion end of the catheter. The cannula slides longitudinally on the catheter so that after a puncture is made, the cannula may be held in position while the catheter is slid the desired length into the body and then is removed from the body by sliding it up the catheter away from the body leaving the catheter still inserted in the body. Although this solves the problem of patient discomfort, the cannula is still positioned around the catheter and could cut or puncture the catheter which is usually made from flexible synthetic resin material.
This problem has been solved by the use of a removable cannula which generally has a longitudinal slit running the length of its body, a longitudinal weakened seam consisting of scoring or perforations opposite the longitudinal slit and wings or finger grips attached thereto as shown in U.S. Pat. Nos. 3,359,978, 3,584,625, 3,592,193, 3,596,658 and 3,598,118. These features combine to permit an operator to peel the cannula off the catheter after it is slid out of the body by bending and breaking it in halves along the longitudinal seam. Thus the cannula is removed entirely and presents no further problem.
However, to date there has been no satisfactory method for making such removable cannulae which have usually been shaped from sheet metal. There is no method available for making such removable cannulae from ordinary cannula stock.